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1
Content available Study of temperature of black holes in terms of Chandrasekhar limit
100%
Mahto D. , Jha B. K. , Singh K. M. , Ram M.
International Letters of Chemistry, Physics and Astronomy
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2015
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tom Vol. 40
43--50
EN
Stephen Hawking gave the formula for the temperature for the black holes as[wzór] . In the present research article, we have converted this formula in terms of Chandrasekhar limit [Mch] and also calculated their values for different test black holes existing in XRBs and AGN. [wzór] Kelvin.
2
Content available Joint detection of gravitational waves from binary black hole and binary neutron star mergers by LIGO and Virgo
100%
Królak A. , Patil M.
Zagadnienia Filozoficzne w Nauce
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2018
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nr 64
95-115
EN
Advanced Virgo detector joined advanced LIGO twin detectors on 1st August 2017 in the quest to look for the gravitational waves. The global network of three detectors was operational for 25 days until the LIGO shut down on 25th August 2017. Two gravitational wave events were registered during this period. One of them was the binary black hole merger dubbed as GW170814 and other one is binary neutron star merger referred to as GW170817. Electromagnetic counterpart associated with binary neutron star merger was promptly identified which marks the beginning of multi-messenger astronomy. This article describes these events emphasizing on the crucial role played by the Virgo and focusing on some methodological issues.
3
Content available remote Pre-low-mass X-ray binaries containing a black hole: investigating a detection mechanism
100%
Bleach J.
Open Physics
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2007
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tom 5
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nr 1
1-10
EN
This work investigates the feasibility of detecting close, detached, black hole-red dwarf binaries, which are expected to be evolutionary precursors of low-mass X-ray binaries (LMXBs). Although this pre-low-mass X-ray binary (pre-LMXB) phase of evolution is predicted theoretically, as yet no such systems have been identified observationally. The calculations presented here suggest that the X-ray luminosity of black hole wind accretion in a pre-LMXB system could exceed the intrinsic X-ray luminosity of the red dwarf secondary star, thereby providing a detection mechanism. However, there is significant uncertainty regarding the efficiency of the conversion of gravitational potential energy to X-ray luminosity resulting from accretion onto a black hole, for example energy may be lost via advection across the event horizon. Still, sources with X-ray luminosities greater than that expected for a red dwarf star, but whose positions coincide with that of a red dwarf would represent candidate pre-LMXB systems. These candidates should be surveyed for the radial velocity shifts that would occur as a result of the orbital motion of a red dwarf star within a close binary system containing a black hole.
4
Content available remote Planck-scale corrections to Friedmann equation
100%
Awad A. , Ali A.
Open Physics
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2014
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tom 12
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nr 4
245-255
EN
Recently, Verlinde proposed that gravity is an emergent phenomenon which originates from an entropic force. In this work, we extend Verlinde’s proposal to accommodate generalized uncertainty principles (GUP), which are suggested by some approaches to quantum gravity such as string theory, black hole physics and doubly special relativity (DSR). Using Verlinde’s proposal and two known models of GUPs, we obtain modifications to Newton’s law of gravitation as well as the Friedmann equation. Our modification to the Friedmann equation includes higher powers of the Hubble parameter which is used to obtain a corresponding Raychaudhuri equation. Solving this equation, we obtain a leading Planck-scale correction to Friedmann-Robertson-Walker (FRW) solutions for the p = ωp equation of state.
5
Content available Black holes: do they exist?
89%
Malec E.
Zagadnienia Filozoficzne w Nauce
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2018
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nr 65
EN
Black holes entered scientific literature as early as at the end of eighteenth century. They had been known at that time as dark stars, but their concept did not find its way to physics or astronomy, and had been abandoned for more than one hundred years. I shall sketch historical developments and discuss present mathematical and observational status of black holes.
6
Content available remote Einstein equation at singularities
88%
Stoica O.-C.
Open Physics
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2014
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tom 12
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nr 2
123-131
EN
Einstein’s equation is rewritten in an equivalent form, which remains valid at the singularities in some major cases. These cases include the Schwarzschild singularity, the Friedmann-Lemaître-Robertson-Walker Big Bang singularity, isotropic singularities, and a class of warped product singularities. This equation is constructed in terms of the Ricci part of the Riemann curvature (as the Kulkarni-Nomizu product between Einstein’s equation and the metric tensor).
7
Content available remote Extreme gravitational lensing in vicinity of Schwarzschild-de Sitter black holes
88%
Bakala P. , Čermák P. , Hledík S. , Stuchlík Z. , Truparová K.
Open Physics
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2007
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tom 5
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nr 4
599-610
EN
We have developed a realistic, fully general relativistic computer code to simulate optical projection in a strong, spherically symmetric gravitational field. The standard theoretical analysis of optical projection for an observer in the vicinity of a Schwarzschild black hole is extended to black hole spacetimes with a repulsive cosmological constant, i.e, Schwarzschild-de Sitterspacetimes. Influence of the cosmological constant is investigated for static observers and observers radially free-falling from the static radius. Simulations include effects of the gravitational lensing, multiple images, Doppler and gravitational frequency shift, as well as the intensity amplification. The code generates images of the sky for the static observer and a movie simulations of the changing sky for the radially free-falling observer. Techniques of parallel programming are applied to get a high performance and a fast run of the BHC simulation code.
8
Content available Polish contribution to space research
75%
Wolański P. , Banaszkiewicz M. , Kłos Z. , Ziółkowski J. , Zdziarski A.
Nauka
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2008
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nr 3
EN
A short historical description of Polish contribution to astronomy and rocket technology is given. Then Polish activities in field of space exploration, such as instrument designed and build in Poland and placed on board of rockets, satellites and space probes during last 50 years are described. Contributions of the Space Research Center of the Polish Academy of Sciences as well as astronomical discoveries made by Polish astrophysicists are presented. Most important missions in which instruments build in Poland were placed on board are among others: Mars Express and Venus Express, Cassini-Huygens, Rosetta and Integral. Among numerous discoveries made by Polish astrophysicists, one should mention the discovery and proper identification of powerful burst from magnetar SGR 1806-20 and the discovery of unusually rapid bursts from black hole Cyg X-1.
9
Content available Genetically modified organisms – economy and safety
75%
Bąkowska-Żywicka K. , Tyczewska A. , Twardowski T.
Nauka
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2008
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nr 3
EN
A short historical description of Polish contribution to astronomy and rocket technology is given. Then Polish activities in field of space exploration, such as instrument designed and build in Poland and placed on board of rockets, satellites and space probes during last 50 years are described. Contributions of the Space Research Center of the Polish Academy of Sciences as well as astronomical discoveries made by Polish astrophysicists are presented. Most important missions in which instruments build in Poland were placed on board are among others: Mars Express and Venus Express, Cassini-Huygens, Rosetta and Integral. Among numerous discoveries made by Polish astrophysicists, one should mention the discovery and proper identification of powerful burst from magnetar SGR 1806-20 and the discovery of unusually rapid bursts from black hole Cyg X-1.
10
Content available Some remarks on the first image of a black hole
65%
Szybka S. J.
Zagadnienia Filozoficzne w Nauce
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2020
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nr 68
281-294
EN
On the 10th of April, 2019 the Event Horizon Telescope Collaboration presented the first image of the black hole. The image was obtained with a planet-scale array of eight ground-based radio telescopes. The observation relied on a technique called very long base interferometry which synchronises telescope facilities around the world. The image of a black hole together with the recent detections of gravitational waves confirms one of the most intriguing predictions of Einstein’s gravity theory, namely, the existence of black holes. I will provide more details on this remarkable observation and explore its consequences for our understanding of nature. The physical reality of black holes is strongly supported by recent advances of astronomy. I claim that this fact is the key to understanding the relation between our world and the world of mathematics.
11
Geniusz Einstein miał rację – Fenomen czarnych dziur istnieje
63%
Bryś H.
Przegląd Geodezyjny
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2023
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tom R. 95, nr 7
9--10
PL
Autor w skrótowej i uproszczonej formie opisuje pierwsze oryginalne obrazy czarnych dziur. Stwierdza, że geometryczna interpretacja obrazów pozwoliła na wyjaśnienie pow-stawania tych od dawna przewidywanych fenomenów. Prezentowane astrofotografie są doskonałym środkiem rejestrowania megadanych z obserwacji kosmicznych oraz naziemnych teleskopów najnowszej generacji - Hubble i Webba. Ten interdyscyplinarny, astrofizyczny problem zjawiska czarnych dziur w kosmosie nie był dotychczas publikowany w żadnym technicznym czasopiśmie krajowym. Aktualnie jest przedmiotem intensywnych badań teoretycznych i obserwacji astronomów. Oryginale zobrazowania NASA/ESA są dowodem oraz potwierdzeniem genialnych hipotez Einsteina opartych na matematycznych teoriach klasycznej fizyki oraz fenomenu niespotykanej dotychczas grawitacji. Publikacja jest syntetycznym opracowaniem rezultatów kilkuletnich studiów literatury przedmiotu, zjawisk kosmicznych oraz badań teoretycznych nad problematyką zjawisk optycznych w głębokim Wszechświecie.
EN
The author briefly and simplified describes the first original images of black holes. He states that the geometrical interpretation of the images allowed to explain the formation of these long-anticipated phenomena. The presented astrophotography is an excellent means of recording megadata from space observations and the latest generation ground-based telescopes - Hubble and Webb. This interdisciplinary, astrophysical problem of the phenomenon of black holes in space has not been published in any technical national journal so far. Currently, it is the subject of intensive theoretical research and astronomical observations. The original NASA/ESA images are proof and confirmation of Einstein's brilliant hypotheses based on the mathematical theories of classical physics and the phenomenon of unprecedented gravity. The publication is a synthetic elaboration of the results of several years of study of the subject literature, cosmic phenomena and theoretical research on the issues of optical phenomena in the deep Universe.
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